The ratio of irises to roses in Nikki's garden is 2:5. She currently has 25 roses. She is planning to add 20 more roses and enough irises to keep the same ratio. How many irises will she have in total after this addition?
Explanation: After adding 20 roses, Nikki will have $25+20=45$ roses.  If she will have 2 irises for every 5 roses, then she will have $2(9)=\boxed{18}$ irises.